1. Field of the Invention
The present invention relates to personal identification devices that verify the identity of a person by checking both a fingerprint pattern and a vein pattern, and relates to electronic apparatuses (such as cellular phone terminals) provided with such personal identification devices.
2. Description of Related Art
In recent years, personal identification devices that check unique biometric information (such as fingerprint patterns, vein patterns, irises, voice patterns, faces, and the shape of hands), instead of passwords or the contents recorded in IC cards, for verifying the identity of a person have come to be used not only in automatic teller machines, electronic commerce systems, and door lock systems for homes and automobiles but also in electronic apparatuses such as cellular phone terminals.
Such a personal identification device checks biometric information that is more difficult to fake than the passwords or IC cards, making it harder for malicious persons to pretend to be someone they are not. This helps greatly improve the security of a system incorporating such a device.
As an example of a conventional technology related to what has been described thus far, various personal identification devices that verify the identity of a person by checking both a fingerprint pattern and a vein pattern have been disclosed and proposed, for example, in JP-A-2005-168627, JP-A-2004-154546, JP-A-2004-054698, JP-A-2003-263640, and JP-A-2002-230553.
The above-mentioned conventional personal identification devices are in general so configured as to read a fingerprint pattern by detecting a component of visible light reflected from the fingertip after being shone thereon and to read a vein pattern by detecting a component of near-infrared light passing through the fingertip or palm after being shone thereon.
Certainly, with the personal identification device that verifies the identity of a person by checking both a fingerprint pattern and a vein pattern, as compared with a configuration in which fingerprint pattern check and vein pattern check are separately performed, it is possible to improve the accuracy of personal identification.
However, with respect to the conventional personal identification device, the following problem arises. As mentioned above, with the conventional personal identification device being so configured as to read a vein pattern by using infrared light and to read a fingerprint pattern by using visible light, there is a possibility that the accuracy with which to read a fingerprint pattern is reduced under circumstances where the light receiving sensor is exposed to natural light (ambient light). This hinders efficient pattern recognition.
In particular, small electronic apparatuses (for example, cellular phone terminals) whose limited space makes it difficult to take structural measures such as covering the light receiving sensor with a light-shielding cover may easily suffer from the above-described problem because, when reading a fingerprint pattern, the natural light easily leaks in the light receiving sensor through a gap between the light receiving sensor and the fingertip.